Endodontic Management of a Two-rooted Mandibular First Premolar with Five Root Canals with Cone-beam Computed Tomography: A Case Report

Proper knowledge of the anatomic structure of the root canal system is a vital prerequisite for successful root canal therapy. This report presents the endodontic management a two-rooted lower first premolar with five root canals. A similar case has not been reported to date. The use of cone beam computed tomography (CBCT) in rare and doubtful cases helps establish an accurate diagnosis and render successful endodontic treatment thereafter. This article helps broaden our knowledge about the possible anatomic diversities as to teeth with more roots and root canals than expected normally.


Introduction
The success of root canal treatment hinges on a thorough knowledge of the root and root canal system morphology and the imaging techniques used to identify all the canals, especially in the lower premolar teeth [1][2].
The majority of mandibular first premolars have one root and one root canal. However, some rather rare variations like two-rooted, three-rooted, and four-rooted premolars have been reported in the literature [3].
Slowey reported that the mandibular premolars are the most complicated teeth concerning endodontic treatment [4]. A study reported the highest failure rate in the mandibular first premolars [5]. A large number of endodontic failures of mandibular premolars have been cited as evidence [5][6].
A possible reason for these failures is the diversity of anatomic variations, which dental practitioners often have limited knowledge about. Hereby, after obtaining informed consent from the patient we report, for the first time, the root canal treatment of a two-rooted mandibular first premolar with five root canals to help broaden the range of possible anatomic variations in the mandibular premolars.    Five root canals were located, and the morphology was confirmed by radiographic examination (Figure 4).

Case Presentation
Working lengths (WL) were established using a Root-ZX apex locator (Morita, Tokyo, Japan), followed by confirmation on a periapical radiograph (Figure 4). Since there were multiple canals in such small area,

Discussion
Mandibular premolars with anatomic variation are the most complicated teeth to perform endodontic treatment [4]. Possible reasons for these complications are the wide range of anatomic variations that are usually not well realized. The complex nature of the root and root canal system morphology of the lower first premolars has been underestimated [3]. The majority of these teeth (97.9%) have a single root. Two roots are found in 1.8% of these teeth and three-rooted (0.2%), and four-rooted (0.1%) varieties are very rare [3]. One root canal is present in 75.8% of the cases, and more root canal systems are present in 24.2% of these teeth [3]. This case report illustrated the unusual anatomy of the roots and root canal system of a mandibular first premolar in an 18-year-old healthy boy, with three roots, which is quite rare (0.2%), and with five root canals, reported here for the first time. Case reports of mandibular first premolars with three roots and three root canals are rare [7][8], and reports of three or more root canals in second premolars are more frequent [9][10]. The coronal anatomy was within the normal limits, with no indication of the variation in the morphology of the root. Based on CBCT images, the other mandibular first premolar (mandibular right first premolar) had two root canals and two roots.
A careful examination of radiographs seems to be necessary when treating mandibular premolars. At least two radiographs with 15° to 20° with either mesial or distal different horizontal angulations are necessary to diagnose multiple root canals in premolar teeth reliably [3].
Sudden narrowing of the main canal on a parallel radiograph indicates root canal multiplicity [11]. However, Martinez-Lozano et al. [12] recommended 40° mesial angulation from the horizontal line as more reliable in finding root canal multiplicity. Moreover, 15° to 30° vertical angular deviation in periapical radiographs is only effective for visualization of root canal system anatomy of mandibular premolars [3]. Radiographs are two-dimensional representation of three-dimensional objects, with unfavorable superimpositions. Interpretations made using two-dimensional radiographs might provide the clinician with information about the unusual anatomy, without showing the different morphological structures and their interrelations [13]. Hoen and Pink [14] found that 42% of teeth needing retreatment had missed roots or root canals. Therefore, it is crucial that all the root canals be identified and debrided during the root canal therapy. CBCT is an extremely useful tool for assessing complex and doubtful anatomies. The value of CBCT in the study of the morphology of complex premolar cases is increasing in clinical endodontics [15][16]. A study concluded that CBCT was superior to other techniques in the identification of multiple root canals in the mandibular first premolars [17]. CBCT might eventually find routine clinical applications in root canal treatment [18][19]. This case report was written after obtaining informed consent from the patient.

Conclusion
Dental clinicians should gain adequate knowledge about the anatomy of the root canal system and its diversities and carry out proper radiographic evaluations before and during root canal treatment. The mandibular first premolar teeth might have extremely complex root and canal system morphology, leading to problems during root canal treatment. CBCT is a valuable diagnostic tool in studying the variations of root and root canal system.

Conflicts of Interest
None